1.\" Copyright (c) 1992, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software developed by the Computer Systems 5.\" Engineering group at Lawrence Berkeley Laboratory under DARPA contract 6.\" BG 91-66 and contributed to Berkeley. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.Dd March 20, 2017 33.Dt KVM_OPEN 3 34.Os 35.Sh NAME 36.Nm kvm_open , 37.Nm kvm_open2 , 38.Nm kvm_openfiles , 39.Nm kvm_close 40.Nd initialize kernel virtual memory access 41.Sh LIBRARY 42.Lb libkvm 43.Sh SYNOPSIS 44.In fcntl.h 45.In kvm.h 46.Ft kvm_t * 47.Fn kvm_open "const char *execfile" "const char *corefile" "const char *swapfile" "int flags" "const char *errstr" 48.Ft kvm_t * 49.Fo kvm_open2 50.Fa "const char *execfile" 51.Fa "const char *corefile" 52.Fa "int flags" 53.Fa "char *errbuf" 54.Fa "int (*resolver)(const char *name, kvaddr_t *addr)" 55.Fc 56.Ft kvm_t * 57.Fn kvm_openfiles "const char *execfile" "const char *corefile" "const char *swapfile" "int flags" "char *errbuf" 58.Ft int 59.Fn kvm_close "kvm_t *kd" 60.Sh DESCRIPTION 61The functions 62.Fn kvm_open , 63.Fn kvm_open2 , 64and 65.Fn kvm_openfiles 66return a descriptor used to access kernel virtual memory 67via the 68.Xr kvm 3 69library routines. 70Both active kernels and crash dumps are accessible 71through this interface. 72.Pp 73The 74.Fa execfile 75argument is the executable image of the kernel being examined. 76This file must contain a symbol table. 77If this argument is 78.Dv NULL , 79the currently running system is assumed, 80as determined from 81.Xr getbootfile 3 . 82.Pp 83The 84.Fa corefile 85argument is the kernel memory device file. 86It can be either 87.Pa /dev/mem 88or a crash dump core generated by 89.Xr savecore 8 . 90If 91.Fa corefile 92is 93.Dv NULL , 94the default indicated by 95.Dv _PATH_MEM 96from 97.In paths.h 98is used. 99It can also be set to a special value 100.Pa /dev/null 101by utilities like 102.Xr ps 1 103that do not directly access kernel memory. 104.Pp 105The 106.Fa swapfile 107argument is currently unused. 108.Pp 109The 110.Fa flags 111argument indicates read/write access as in 112.Xr open 2 113and applies only to the core file. 114Only 115.Dv O_RDONLY , 116.Dv O_WRONLY , 117and 118.Dv O_RDWR 119are permitted. 120.Pp 121The 122.Nm kvm 123library provides two different error reporting mechanisms. 124One provides backward compatibility with the SunOS kvm library, while the 125other provides an improved error reporting framework. 126The mechanism used by a descriptor is determined by the function used to 127open the descriptor. 128.Pp 129The 130.Fn kvm_open 131function is the Sun kvm compatible open call. 132Here, the 133.Fa errstr 134argument indicates how errors should be handled. 135If it is 136.Dv NULL , 137no errors are reported and the application cannot know the 138specific nature of the failed kvm call. 139If it is not 140.Dv NULL , 141errors are printed to 142.Dv stderr 143with 144.Fa errstr 145prepended to the message, as in 146.Xr perror 3 . 147Normally, the name of the program is used here. 148The string is assumed to persist at least until the corresponding 149.Fn kvm_close 150call. 151.Pp 152The 153.Fn kvm_open2 154and 155.Fn kvm_openfiles 156functions provide 157.Bx 158style error reporting. 159Here, error messages are not printed out by the library. 160Instead, the application obtains the error message 161corresponding to the most recent kvm library call using 162.Fn kvm_geterr 163(see 164.Xr kvm_geterr 3 ) . 165The results are undefined if the most recent kvm call did not produce 166an error. 167Since 168.Fn kvm_geterr 169requires a kvm descriptor, but the open routines return 170.Dv NULL 171on failure, 172.Fn kvm_geterr 173cannot be used to get the error message if open fails. 174Thus, 175.Fn kvm_open2 176and 177.Fn kvm_openfiles 178will place any error message in the 179.Fa errbuf 180argument. 181This buffer should be _POSIX2_LINE_MAX characters large (from 182<limits.h>). 183.Pp 184The 185.Fa resolver 186argument points to a function used by the 187.Nm kvm 188library to map symbol names to kernel virtual addresses. 189When the 190.Fa resolver 191function is called, 192.Fa name 193specifies the requested symbol name. 194If the function is able to resolve the name to an address, 195the address should be set in 196.Fa addr 197and the function should return zero. 198If the function is not able to resolve the name to an address, 199it should return a non-zero value. 200When opening a native kernel image, 201.Fa resolver 202may be set to 203.Dv NULL 204to use an internal function to resolve symbol names. 205Non-native kernel images 206.Pq such as when cross-debugging a crash dump 207require a valid 208.Fa resolver . 209.Sh RETURN VALUES 210The 211.Fn kvm_open , 212.Fn kvm_open2 , 213and 214.Fn kvm_openfiles 215functions return a descriptor to be used 216in all subsequent kvm library calls. 217The library is fully re-entrant. 218On failure, 219.Dv NULL 220is returned, in which case 221.Fn kvm_open2 222and 223.Fn kvm_openfiles 224write the error message into 225.Fa errbuf . 226.Pp 227.Rv -std kvm_close 228.Sh ERRORS 229The 230.Fn kvm_close 231function may fail and set the global variable 232.Va errno 233for any of the errors specified for 234.Xr close 2 . 235.Pp 236The 237.Fn kvm_close 238function may also fail and set 239.Va errno 240if: 241.Bl -tag -width Er 242.It Bq Er EINVAL 243The value passed via 244.Fa kd 245was 246.Dv NULL . 247.El 248.Sh SEE ALSO 249.Xr close 2 , 250.Xr open 2 , 251.Xr kvm 3 , 252.Xr kvm_getargv 3 , 253.Xr kvm_getenvv 3 , 254.Xr kvm_geterr 3 , 255.Xr kvm_getprocs 3 , 256.Xr kvm_native 3 , 257.Xr kvm_nlist 3 , 258.Xr kvm_read 3 , 259.Xr kvm_write 3 , 260.Xr kmem 4 , 261.Xr mem 4 262.Sh BUGS 263There should not be three open calls. 264The ill-defined error semantics 265of the Sun library and the desire to have a backward-compatible library 266for 267.Bx 268left little choice. 269.Sh HISTORY 270The 271.Fn kvm_open2 272function first appeared in 273.Fx 11.0 . 274